Process for preparing 3-hydroxy-isoxazole derivative

ABSTRACT

A process for preparing 3-hydroxy-isoxazole compounds of the formula:   WHEREIN R1 represents a member selected from the group consisting of an hydrogen atom, an alkyl group, an aryl group, and an aryl group substituted with a member selected from the group consisting of a halogen atom, a nitro group and a lower alkyl group, which comprises reacting in the presence of a suitable solvent and at a temperature of from -20*C to 70*C, a compound of the formula:   WHEREIN R1 is defined as above, and R2 and R3 represent lower alkyl groups, with hydroxylamine in the presence of an alkali, subsequently treating the reaction product with acid, and then separating the acidified reaction product from the reaction system is disclosed.

United States Patent 11 1 Imamura et al.

1 1 Jan. 14, 1975 PROCESS FOR PREPARING S-HYDROXY-ISOXAZOLE DERIVATIVE [75] Inventors: Kennosuke Imamura; Toshio Kikuchi, both of Tokyo; Shunichi Kanazawa, Chiba, all of Japan [73] Assignee: Nippon Chemical Industrial Co.,

Ltd., Tokyo, Japan 22 Filed: 011.24, 1972 21 Appl. No.: 300,089

[30] Foreign Application Priority Data Oct, 23, 1971 Japan 46-83679 [52] US. Cl 260/307 H, 260/521 R, 260/521 A,

260/535 R, 260/559 R, 260/56l- N [51] Int. Cl C07d 85/22 [58] Field of Search 260/307 H, 307 A [56] References Cited UNITED STATES PATENTS 3,687,968 8/1972 lwai et a]. 260/307 H Primary Examiner-Raymond V. Rush Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak ABSTRACT A process for preparing 3-hydroxy-isoxazole compounds of the formula:

R c CH COOR wherein R is defined as above, and R and R represent lower alkyl groups, with hydroxylamine in the presence of an alkali, subsequently treating the reaction product with acid, and then separating the acidified reaction product from the reaction system is disclosed.

3 Claims, No Drawings 3 860,60 3 1 2 PROCESS FOR PREPARING SUMMARY OF THE INVENTION 3'HYDROXY'ISOXAZOLE DERIVATIVE As the result of studies in the light of these defects,

BACKGROUND OF THE INVENTION applicants have discovered that these 3-hydroxyisoxazole derivatives can easily be produced by the re- 1. Field of the Invention 5 action between a beta-alkoxyacrylate derivative and The present inventlon relates to a process for preparhydroxylamine. mg certain 3-hydroxy-isoxazole derivatives represented That is, the present invention relates toga process for by the general formula:

preparing 3-hydroxy-isoxazole derivatives represented 01- by the above general formula (I), which comprises re- U x (I) arctmg a belti-alkolxyacrylate derivative represented by R O t e genera ormu a.

wherein R, represents a hydrogen atom, an alkyl group, R c CH COOR (11) an aryl group, or an aryl group substituted by a halogen 1 3 atom, a nitro group or a lower alkyl group. OR

2. Description of the Prior Art 2 As a process for producing 3-hydroxy-isoxazole derivatives on an industrial scale, there have hitherto wherein R,representsahydrogen atom,an alkylgroup, been known the process of, for example, reactinga prO- an aryl group, an aryl group substituted by a halogen piolic acid alkyl ester with hydroxylamine in the presatom, a nitro group or a lower alkyl group, and R and ence of an alkali metal hydroxide (Japanese Patent R represent the same or different lower alkyl groups, Publication No. 25660/67); the process of reacting an with hydroxylamine in the presence of an alkali, and alpha, beta-halogen substituted carboxylic acid ester subsequently treating the reaction product with an derivative, with hydroxylamine in the presence of an acid. In the above general formula (H), where R,, R alkali metal hydroxide, etc. (Japanese Patent Publicaand R represent alkyl groups, they preferably contain tion No. 14704/68), and similar processes. 1-4 carbon atoms.

However, all of the above-described processes are accompanied by considerable difficulties when prac- DETAILED DESCRIPTION OF THE INVENTION ticed on an industrial scale. For example, in the former The process in accordance with the present invention process, the starting material, the propiolic acid alkyl is illustrated by the following reaction schematic diaester derivative, is hardly available industrially. gram:

ll R -C CH-COOR NHZOH -9 R 4; CH-CNHOH+R3OH...(1)

OR CR 2 H I H R -C CH-CNHOH N R OH ..(Z)

Therefore, in the latter process, alpha, beta-halogen In the above formulae, R R and R are the same as substituted carboxylic acid ester derivatives are used as defined above. the starting material which substantially produces said As the typical starting material to be used in this inmaterial. However, a large amount of alkali is required vention and represented by the above general formula in the reaction with the hydroxylamine. That is, since (II), there are illustrated, for example, those as follows:

hydroxylamine is usually used in the form of hydrochlomethyl beta-methoxyacrylate; ethyl betaride or sulfate, the amount of alkali directly necessary methoxyacrylate; methyl beta-ethoxyacrylate; ethyl for the present reaction and the amount of dehybeta-ethoxyacrylate; methyl beta-methyl, betadrohalogenating agent required is great. Therefore the methoxyacrylate; ethyl beta-methyl, betalatter process requires the alkali in an amount of at methoxyacrylate; propyl beta-methyl, betaleast 2 times that in the former process. Thus, there will methoxyacrylate; butyl beta-methyl, betabe formed a large amount of salt as a by-product, remethoxyacrylate; methyl beta-methyl, betasulting in the loss of the end product upon separation ethoxyacrylate; ethyl beta-methyl, beta-ethoxyacrylate; due to the adsorption or adhesion of the product to the methyl beta-methyl, beta-propoxyacrylate; ethyl beta- 1 methyl, beta-propoxyacrylate; methyl beta-ethyl, beta- Besides, these reactions require a comparatively long methoxyacrylate; ethyl beta-ethyl, betareaction time, and thus, they have considerable probmethoxyacrylate; methyl beta-ethyl, betalems from an industrial standpoint. ethoxyacrylate; ethyl beta-ethyl, beta-propoxyacrylate;

ethyl beta-propyl, beta-methoxyacrylate; ethyl betabutyl, beta-methoxyacrylate, ethyl beta-phenyl, betamethoxyacrylate; ethyl beta-phenyl, betaethoxyacrylate; ethyl beta-(4-chlorophenyl), betamethoxyacrylate; ethyl beta-(4-bromophenyl), betaethoxyacrylate; ethyl beta-(4-nitrophenyl), betamethoxyacrylate; ethyl beta-(4-methylphenyl), betaethoxyacrylate; etc.

On the other hand, the other starting material, hydroxylamine, may be used in the usually available form of a salt neutralized with hydrochloric acid, sulfuric acid, and other suitable neutralizing acids.

As described above, the reaction of this invention is a dealcoholization reaction, and hence, in practice, it is particularly preferable to use water, a lower alcohol, such as methanol, ethanol and propanol, or a mixture thereof as the solvent. However, other solvents may also be used provided they are inert in the reaction of this invention. Therefore, the solvents to be used are not particularly limited to those described above.

In carrying out the reaction of the present invention, the reaction temperature may be in the range of from 20C to 70C, but normally a temperature of from the ordinary room temperature to about 60C is practical and preferred.

in general, the reaction temperature in the second step of the ring closure by acid treatment is preferably a little higher than that in the first step of producing the hydroxamic acid derivative according to the reaction of the above formula (1). In the reaction, special heating is not necessary, and the reaction can be conducted by adjusting the reaction temperature. In many cases, if the reaction temperature is lower than room temperature, the reaction rate becomes slow, while, if the temperature is raised to the temperature higher than is necessary, the end product becomes subject to decomposition.

Since the reaction rate of the reaction of the present invention is faster than that of the conventional reactions, the reaction time necessary for the completion thereof is shorter than that in the conventional processes. A reaction time of from 0.5-6 hours is therefore satisfactory. As the alkali to be used in the first step of the reaction of this invention, hydroxides of alkali metals, such as sodium hydroxide, potassium hydroxide, etc., alkali metal alcoholates, ammonia, and the like are practical. On the other hand, as the acid to be used in the second step, mineral acids, such as hydrochloric acid and sulfuric acid, or organic acids such as formic acid, acetic acid, etc., are suitable, which may be used in combination.

The first step of the invention is conducted using substantially a stoichiometric amount of reactants but in many cases, hydroxylamine is used in an equivalent or a little excessive amount per mole of the compound of the foregoing formula (II). The alkali to be present is used in an amount of 1 mole or a slightly excessive amount per 1 mole of hydroxylamine. In this case, the presence of a particularly excessive amount of alkali does not substantially affect the reaction of the invention. However, considering the separation of the salt to be formed, to use a substantially excessive amount of alkali is preferably avoided.

In the present invention, the first and the second steps are conducted continuously, but in some cases, the by-product salt may be separated in the course thereof.

Thus, after the completion of the reaction, the end product can be obtained .by the usual operation ofscpa ration and purification. For example, the by-product salt is separated by filtration, the solvent is distilled off, and the end product is extracted with ether and, if nee essary, recrystallized. Thus, there can he obtained the end product.

As described above, in the process in accordance with the invention, a beta-alkoxyacrylate is used as a starting material, which is comparatively easily available industrially, the reaction time is shortened, and the alkali is used in a smaller amount as compared with conventional processes used to date to prepare the desired compounds. Therefore, the process ofthe present invention is advantageous from an industrial standpoint. Furthermore, since the reaction of the invention is a dealcoholization reaction, the alcohol by-product itself can advantageously be the reaction solvent, which is considered to be of merit in operation.

Now, the present invention will be described in greater detail below by reference to the Examples, which follow but by no means are these Examples deemed limitive of the same.

EXAMPLE 1 ml ofa methanol solution in which 0.1] mole of hydroxylamine hydrochloride had been dissolved was placed in a reaction vessel, and amcthanol solution containing 0.22 mole of potassium hydroxide was then added dropwise thereto at room temperature under stirring. After stirring for a while, 0.! mole of methyl beta-methyl, beta-methoxyacrylate was added dropwise thereto, and the stirring was continued for 3-4 hours at room temperature. Subsequently, the pH of the reaction system was adjusted to l by blowing hydrochloric acid gas therethrough and the system was maintained at that state for a while. After completion of the reaction, the reaction solution was filtrated to separate the by-product salt, potassium chloride, and the filtrate was distilled to remove methanol, Subsequently, the residue was extracted with 50cc of toluene. Upon distilling off the solvent, there was obtained 6.5 g of yellow, crystalline 3-hydroxy-5- methylisoxazole (in 65.7% yield).

Elemental analysis: ('A) C H N Calculated: 48.48 5.09 I414 Found: 421.31 5.10 14.21

EXAMPLE 2 0.11 mole of hydroxylamine hydrochloride and 0.22 mole of potassium hydroxide were reacted with each other in ethanol and, after stirring for a while, ().l mole of ethyl beta-phenyl, beta-methoxyacrylate was added dropwise thereto at room temperature. After stirring for a further 3-4 hours, hydrochloric acid gas was blown therethrough to adjust the pH to I. Then, sepa ration and extraction were conducted in the same manner as in Example 1 to thereby obtain 4.6 g of white, columnar crystals of 3-hydroxy-5-phcnylisoxazole (in 41.4% yield).

wherein R, represents a member selected from the group consisting of a hydrogen atom, C -C alkyl, phenyl and phenyl substituted with a member selected from the group consisting of a halogen atom, nitro and C -C alkyl, which comprises reacting in the presence EXAMPLES 3 8 ofa solvent selected from the group consisting of H 0, Various 3-hydroxyisoxazole derivatives were synthe- CH OH, C H Ol-l, C H OH and mixtures thereof and at sized by the same procedure as in Example 1. The reaca temperature of from 20C to 70C, a compound of tion conditions and the results thereof are given in the the formula: following Table.

Table I Example Starting mole Hydroxylmole Alkali (mole) Acid (pH) Temp.C Time (hr) End Yield No. material amine product 3 a 0.1 HCI salt 0.11 KOH 0.20 HCl gas 1.0 50 2 4 A 36.5 4 b 0.1 do. 0.11 do. 0.13 do. 1.5 -40 2 4 B 68.4 5 c 0.1 11,50. Sal! 0.12 do. 0.22 H 50, 1.0 20-40 2 4 C 62.5 6 d 0.1 HCl Sal! 012 NH: 0.23 1-1c1 gas 1.0 20 50 2 4 D 52.8 7 e 0.1 11,50, salt 0.11 CH ONa 0.21 11,50, 10 20-50 2 5 E 46.3 8 f 0.1 HCl salt 0.12 KOH 0.25 HCI gas 1.0 20-50 2 5 F 32.5

(Starting material) a: Ethyl beta-methoxyacrylate b: Butyl beta-methyl. beta-methoxyacrylate C: Ethyl beta-ethyl. beta-propoxyacrylate d: Methyl beta-phenyl. beta-ethoxyacrylate e: Ethyl he1a-(4-chl0r0phenyl). beta-m ethoxyacrylate f: Ethyl be1a-(4-methylphenyl). beta-methoxyacrylate End product A: 3-Hydr0xy-isoxazule B: S-Hydrnxy-S-methyl-isnnzole C'. B-Hydroxy-Sathyl-isoxaznle D: 3-Hydroxy-S-phnyl-isoxuole E: 3-Hydroxy-S-(m-chlorophenyl)-isoxazole F: 3-Hydroxy-5(4-methylphenylHsoxazole EXAMPLE 9 R C\J CH COOR 100 ml of propanol containing 0.11 mole of hydrox- O ylamine hydrochloride was placed in a reaction vessel, 2

I l d proparlol Solutlon Contammg m potas wherein R is defined as above, and R and R represent sium hydroxide was then added dropw1se t ereto at th 0 e same or different C,C, alkyl groups, with hydrox- 30 C under stirrlng. After stirring for a while, 0.1 mole ylamme 1n the presence of an alkali selected from the of methyl beta-methyl, beta-propoxyacrylate was r of k t l h d added dropwise thereto, and stirring was continued for P g i l fi i 3-4 hours at 2040C. Subsequently, hydrochloric 40 g y 3 8 d a me a 5 O l d acid gas was blown into the reaction system to adjust g f y trfiatmgt e gH s the pH thereof to l, and the reaction system was main- Se ecte fr f e ilp Consisting 0 h I ill? 4 a tained in that state for a while under stirring. After Ilmturet ere) iandt en SeParamlgt e dcld' led redc completion of the reaction, the reaction solution was Product from the {636mm y f filtrated to separate out the potassium chloride, and the The PmcwS of Clam whcremosald temperature end product was separated and purified in a convenranges fmm mom temperafurc to 60 tional manner to thereby obtain 6.91 g of yellow, crys- The Procgss of Clalm Whcrfiln 881d bellitalline 3-hydroxy-S-methyl-isoxazole (in 69.8% yield). alkoxyacrylate q p 1S a member Selected from the group consisting of methyl beta-methoxyacrylate, Elememal C H N ethyl beta-methoxyacrylate, methyl beta- Calculated: 48.48 5.09 14.14 ethoxyacrylate, ethyl beta-ethoxyacrylate, methyl beta- Fvundi 43-45 14-16 methyl-beta-methoxyacrylate, ethyl beta-methyl-betamethoxyacrylate, propyl beta-methyl-betamethoxyacrylate, butyl beta-methyl-beta- The compounds prepared by this processare used as methoxyacrylate, methyl beavmethypbcub mermcd'ate rawtnlatenals h Preparanon of ethoxyacrylate, ethyl beta-methyl-beta-ethoxyacrylate, Cultural and medlcmal f l methyl beta-methyl-beta-propoxyacrylate, ethyl beta- Although the present nventionhas been adequately methyl beta propoxyacrylatey methyl bem ethyl beta described in the foregoing specification and examples methoxyauylate, h l beta-ethyl-betaincluded therein, it is readily apparent that various 0 methoxyacrylate, methyl beta ethyl beta charlges and modlffcfmons can be made wlthout ethoxyacrylate, ethyl beta-ethyl-beta-propoxyacrylate, Pamng f 9 and scope thereof ethyl beta-propyl-beta-methoxyacrylate, ethyl beta- What Clalmed butyl-beta-methoxyacrylate, ethyl beta-phenyl-betal. A process for preparing 3-hydroxy1soxazole comh l te, ethyl beta-phenyl-b PoundS of the formulai ethoxyacrylate, ethyl beta-(4-chlorophenyl)-betamethoxyacrylate, ethyl beta-(4-bromophenyl )-betaethoxyacrylate, ethyl beta-( 4-nitrophenyl )-betamethoxyacrylate, and ethyl beta-(4 methylphenyl)- beta-ethoxyacrylate. 

2. The process of claim 1, wherein said temperature ranges from room temperature to 60*C.
 3. The process of claim 1, wherein said beta-alkoxyacrylate compound is a member selected from the group consisting of methyl beta-methoxyacrylate, ethyl beta-methoxyacrylate, methyl beta-ethoxyacrylate, ethyl beta-ethoxyacrylate, methyl beta-methyl-beta-methoxyacrylate, ethyl beta-methyl-beta-methoxyacrylate, propyl beta-methyl-beta-methoxyacrylate, butyl beta-methyl-beta-methoxyacrylate, methyl beta-methyl-beta-ethoxyacrylate, ethyl beta-methyl-beta-ethoxyacrylate, methyl beta-methyl-beta-propoxyacrylate, ethyl beta-methyl-beta-propoxyacrylate, methyl beta-ethyl-beta-methoxyacrylate, ethyl beta-ethyl-beta-methoxyacrylate, methyl beta-ethyl-beta-ethoxyacrylate, ethyl beta-ethyl-beta-propoxyacrylate, ethyl beta-propyl-beta-methoxyacrylate, ethyl beta-butyl-beta-methoxyacrylate, ethyl beta-phenyl-beta-methoxyacrylate, ethyl beta-phenyl-beta-ethoxyacrylate, ethyl beta-(4-chlorophenyl)-beta-methoxyacrylate, ethyl beta-(4-bromophenyl)-beta-ethoxyacrylate, ethyl beta-(4-nitrophenyl)-beta-methoxyacrylate, and ethyl beta-(4-methylphenyl)-beta-ethoxyacrylate. 